We investigate the possibility of nearly equally spaced periods in 13 hot subdwarf B (sdB) stars observed with the Kepler spacecraft and one observed with CoRoT. Asymptotic limits for gravity (g-)mode pulsations provide relationships between equal-period spacings of modes with differing degrees and relationships between periods of the same radial order n but differing degrees . Period transforms, Kolmogorov-Smirnov tests and linear least-squares fits have been used to detect and determine the significance of equal-period spacings. We have also used Monte Carlo simulations to estimate the likelihood that the detected spacings could be produced randomly.Period transforms for nine of the Kepler stars indicate = 1 period spacings, with five also showing peaks for = 2 modes. 12 stars indicate = 1 modes using the Kolmogorov-Smirnov test while another shows solely = 2 modes. Monte Carlo results indicate that equal-period spacings are significant in 10 stars above 99 per cent confidence, and 13 of the 14 are above 94 per cent confidence. For 12 stars, the various methods find consistent period spacings to within the errors, two others show some inconsistencies, likely caused by binarity, and the last has significant detections but the mode assignment disagrees between the methods.We use asymptotic period spacing relationships to associate observed periods of variability with pulsation modes for = 1 and 2. From the Kepler first-year survey sample of 13 multiperiodic g-mode pulsators, five stars have several consecutive overtones making period spacings easy to detect, six others have fewer consecutive overtones but period spacings are readily detected, and two stars show marginal indications of equal-period spacings. We also

We present results from the first two quarters of a survey to search for pulsations in compact stellar objects with the Kepler spacecraft. The survey sample and the various methods applied in its compilation are described, and spectroscopic observations are presented to separate the objects into accurate classes. From the Kepler photometry we clearly identify nine compact pulsators and a number of interesting binary stars. Of the pulsators, one shows the strong, rapid pulsations typical of a V361 Hya‐type sdB variable (sdBV); seven show long‐period pulsation characteristics of V1093 Her‐type sdBVs; and one shows low‐amplitude pulsations with both short and long periods. We derive effective temperatures and surface gravities for all the subdwarf B stars in the sample and demonstrate that below the boundary region where hybrid sdB pulsators are found, all our targets are pulsating. For the stars hotter than this boundary temperature a low fraction of strong pulsators (<10 per cent) is confirmed. Interestingly, the short‐period pulsator also shows a low‐amplitude mode in the long‐period region, and several of the V1093 Her pulsators show low‐amplitude modes in the short‐period region, indicating that hybrid behaviour may be common in these stars, also outside the boundary temperature region where hybrid pulsators have hitherto been found.

The survey phase of the Kepler Mission includes a number of hot subdwarf B (sdB) stars to search for non‐radial pulsations. We present our analysis of two sdB stars that are found to be g‐mode pulsators of the V1093 Her class. These two stars also display the distinct irradiation effect typical of sdB stars with a close M‐dwarf companion with orbital periods of less than half a day. Because the orbital period is so short, the stars should be in synchronous rotation, and if so, the rotation period should imprint itself on the multiplet structure of the pulsations. However, we do not find clear evidence for such rotational splitting. Though the stars do show some frequency spacings that are consistent with synchronous rotation, they also display multiplets with splittings that are much smaller. Longer‐duration time series photometry will be needed to determine if those small splittings are in fact rotational splitting, or caused by slow amplitude or phase modulation. Further data should also improve the signal‐to‐noise ratio, perhaps revealing lower‐amplitude periodicities that could confirm the expectation of synchronous rotation. The pulsation periods seen in these stars show period spacings that are suggestive of high‐overtone g‐mode pulsations.

We present the discovery of non‐radial pulsations in five hot subdwarf B (sdB) stars based on 27 d of nearly continuous time series photometry using the Kepler spacecraft. We find that every sdB star cooler than ≈27 500 K that Kepler has observed (seven so far) is a long‐period pulsator of the V1093 Her (PG 1716) class or a hybrid star with both short and long periods. The apparently non‐binary long‐period and hybrid pulsators are described here. The V1093 Her periods range from 1 to 4.5 h and are associated with g‐mode pulsations. Three stars also exhibit short periods indicative of p‐modes with periods of 2–5 min and in addition, these stars exhibit periodicities between both classes from 15 to 45 min. We detect the coolest and longest‐period V1093 Her‐type pulsator to date, KIC010670103 (Teff≈ 20 900 K, Pmax≈ 4.5 h) as well as a suspected hybrid pulsator, KIC002697388, which is extremely cool (Teff≈ 23 900 K) and for the first time hybrid pulsators which have larger g‐mode amplitudes than p‐mode ones. All of these pulsators are quite rich with many frequencies and we are able to apply asymptotic relationships to associate periodicities with modes for KIC010670103. Kepler data are particularly well suited for these studies as they are long duration, extremely high duty cycle observations with well‐behaved noise properties.

We present five new pulsating subdwarf B (sdB) stars discovered by the Kepler spacecraft during the asteroseismology survey phase. We perform time series analysis on the nearly continuous month-long Kepler data sets of these five objects; these data sets provide nearly alias-free time series photometry at unprecedented precision. Following an iterative prewhitening process, we derive the pulsational frequency spectra of these stars, separating out artefacts of known instrumental origin. We find that these new pulsating sdB stars are multiperiodic long-period pulsators of the V1093 Her type, with the number of periodicities ranging from eight (KIC 8302197) to 53 (KIC 11558725). The frequencies and amplitudes are typical of g-mode pulsators of this type. We do not find any evidence for binarity in the five stars from their observed pulsation frequencies. As these are g-mode pulsators, we briefly looked for period spacings for mode identification and found average spacings of about 260 and 145 s. This may indicate l = 1 and 2 patterns. Some modes may show evidence of rotational splitting. These discoveries complete the list of compact pulsators found in the survey phase. Of the 13 compact pulsators, only one star was identified as a short-period (p-mode) V361 Hya pulsator, while all other new pulsators turned out to be V1093 Her class objects. Among the latter objects, two of them seemed to be pure V1093 Her while the others show additional low-amplitude peaks in the p-mode frequency range, suggesting their hybrid nature. Authenticity of these peaks will be tested with longer runs currently under analysis.